Three Sisters Springs in Crystal River, Florida, is widely known by underwater photographers and snorkelers for its resident manatees — but this week, these “mermaids” took over the marine sanctuary by storm.

According to USA Today, roughly 300 manatees huddled together in Three Sisters Springs on Monday. This massive aggregation resulted in a one-acre closure of the springs, USA Today reported, but the area has since been reopened until the manatees return during the next tidal change.

A migratory species, West Indian Manatees spend the winter months in shallow, slow-moving, Florida waters — including estuaries, canals, rivers and coastal areas — and they are known to travel to Three Sisters Springs annually during high tides.

On Jan. 7, 2016, the U.S. Fish and Wildlife Service announced a proposal for a change in classification of the West Indian Manatee from endangered to threatened under the Endangered Species Act. According to the FWS website, this classification “will not affect federal protections currently afforded by the ESA,” and said that conservation efforts to fully recover manatee populations will continue.

“It is probably safe to say that Florida’s manatee population is in recovery,” says Miles Saunders, Media Relations and Marketing Specialist for Visit Citrus. “Last year’s statewide synoptic survey reported 6,063 manatees in Florida. Contrast that to the first year of that survey in 1991 when there were 1,267. This January, the U.S. Fish and Wildlife Service’s Joyce Kleen reported 1,042 manatees in Kings Bay and the Homosassa River alone.”

Though this is not the largest manatee aggregation recorded in Three Sisters, 2016 has been a record-breaking one for manatee populations in Citrus County and King’s Bay. After an aerial survey by Crystal River Wildlife Refuge on Jan. 12, refuge biologist Joyce Kleen reported an all-time record of 1,042 manatees across a survey route spanning from the Crystal River Power Plant to Blue Waters in Homosassa. The previous record was 1,016 manatees in February 2015.